/**
  * Author: Mei
  * Date: 2020-11-22 15:32
  * Description: 
  *
  */
#include <queue>
#include <memory>
#include <mutex>
#include <condition_variable>
#include <iostream>
#include <thread>

template<typename T>
class threadsave_queue {
private:
    mutable std::mutex mut;//必须是mutable，因为empty是const方法，但是要锁mut，锁操作就是改变操作
    std::queue<T> data_queue;
    std::condition_variable data_cond;
public:
    threadsave_queue() {}

    threadsave_queue(threadsave_queue const &other) {
        std::lock_guard<std::mutex> lk(other.mut);
        data_queue = other.data_queue();
    }

    void push(T new_value) {
        std::lock_guard<std::mutex> lk(mut);
        data_queue.push(new_value);
        data_cond.notify_one();
    }

    void wait_and_pop(T &value) {
        std::unique_lock<std::mutex> lk(mut);
        data_cond.wait(lk, [this] { return !data_queue.empty(); });
        value = data_queue.front();
        data_queue.pop();
    }

    std::shared_ptr<T> wait_and_pop() {
        std::unique_lock<std::mutex> lk(mut);
        data_cond.wait(lk, [this] { return !data_queue.empty(); });
        std::shared_ptr<T> res(std::make_shared<T>(data_queue.front()));
        data_queue.pop();
        return res;
    }

    bool empty() const {
        std::lock_guard<std::mutex> lk(mut);
        return data_queue.empty();
    }
};

void make_data(threadsave_queue<int> &tq, int val) {
    tq.push(val);
}

void get_data1(threadsave_queue<int> &tq, int &d1) {
    tq.wait_and_pop(d1);
}

void get_data2(threadsave_queue<int> &tq, int &d1) {
    auto at = tq.wait_and_pop();
    d1 = *at;
}
//多线程 利用条件变量实现线程安全的队列
int main() {
    threadsave_queue<int> q1;
    int d1;
    std::thread t1(make_data, std::ref(q1), 10);
    std::thread t2(get_data1, std::ref(q1), std::ref(d1));
    t1.join();
    t2.join();
    std::cout << d1 << std::endl;
    std::thread t3(make_data, std::ref(q1), 20);
    std::thread t4(get_data2, std::ref(q1), std::ref(d1));
    t3.join();
    t4.join();
    std::cout << d1 << std::endl;
    q1.empty();

}